divalproex sodium

“FORMULATION DEVOLOPMENT AND EVALUATION OF DIVALPROEX SODIUM EXTENDED RELEASE TABLET”

BY

V V GANESH P

Dissertation submitted to

KLE Academy of Higher Education & Research– Deemed University, Belgaum,

Karnataka

In partial fulfilment of the requirements for the degree of

MASTER OF PHARMACY

IN

PHARMACEUTICS

Under the guidance of

Dr. B.G.DESAI

Department of Pharmaceutics

KLE University’s College of Pharmacy, Bangalore- 5660010

2013

KLE ACADEMY OF HIGHER EDUCATION AND RESEARCH

- DEEMED UNIVERSITY, BELGAUM, KARNATAKA

DECLARATION BY THE CANDIDATE

I hereby declare that this dissertation entitled


is a bonafide and genuine research work carried out by me under the guidance

of Dr. B.G.DESAI Professor, Department of Pharmaceutics, KLE

University’s College of Pharmacy, Bangalore.

Date:

Place: Bangalore V V GANESH P

KLE UNIVERSITY’S COLLEGE OF PHARMACY,

BANGALORE-560010

(A constituent unit of KLE Academy of Higher Education and

Research – Deemed University)

CERTIFICATE BY THE GUIDE

This is to certify that the dissertation entitled

“FORMULATION DEVOLOPMENT AND EVALUATION OF DIVALPROEX EXTENDED RELEASE TABLET”

is a bonafide research work done by V V GANESH P under my

supervision and guidance, in partial fulfilment of the requirement for

the award of degree of MASTER OF PHARMACY IN PHARMACEUTICS.

Date:

Place: Bangalore

Dr. B.G.DESAI

Professor Department of Pharmaceutics

KLE University’s College of Pharmacy

Rajajinagar, Bangalore-560010


BANGALORE-560010

(A constituent unit of KLE Academy of Higher Education and Research –

Deemed University)

ENDORSEMENT BY THE HEAD OF THE DEPARTMENT



is a bonafide and genuine research work carried out by V V GANESH P. under

the guidance of Dr. B.G.DESAI Professor, Department of Pharmaceutics,

KLE University’s College of Pharmacy, Bangalore.

Date:

Place: Bangalore

Dr. H. N. SHIVAKUMAR

Professor & Head of Department Department of Pharmaceutics




BANGALORE-560010

(A constituent unit of KLE Academy of Higher Education and Research –

Deemed University)

ENDORSEMENT BY THE HEAD OF THE INSTITUTION



is a bonafide and genuine research work carried out by V V GANESH P. under

the guidance of Dr. B.G.DESAI Professor, Department of Pharmaceutics,

KLE University’s College of Pharmacy, Bangalore.

Date:

Place: Bangalore

Dr. B.G.DESAI

PRINCIPAL Department of Pharmaceutics



ACKNOWLDGEMENT

I have worked with a great number of people whose contribution in

assorted ways to the research and the making of the thesis deserved special

mention. It is a pleasure to convey my gratitude to them all in my humble

acknowledgment.

I would like to first express my gratitude & indebtedness, to my Parents

Lt. Mr. P VENU & Mrs. P VASUNDHARA, whose love and support made this

day possible in my life. There are no words, which can express my gratitude

towards my brother SUBHASH, my uncle & aunt Mr. P VENKATESWARAO &

Mrs. P LAKSHMI and also my sisters YAMIKA & RACHALA for their

constant support, immense care, faith in me and divine love towards me, which

made my dream come true.

I would like to record my gratitude to my gracious mentor Dr. B. G.

Desai, Guide and Principal, K.L.E. University’s College of Pharmacy,

Bangalore, for his supervision, advice and guidance from the very early stage of

this research as well as giving me extraordinary experiences throughout the

work. Above all and the most needed, he provided me unflinching encouragement

and support in various ways. His truly scientist intuition has made him as a

constant oasis of ideas and passions in science, which exceptionally inspire and

enrich my growth as a student, a researcher and a scientist want to be. I am

indebted to him more than he knows.

I wish to express my sincere thanks, with a deep sense of gratitude to

Dr. H. N. Shivakumar, Dr. Uma A Patil, Mrs. Preeti G.B, Mrs. Anasuya

Patil. Department of Pharmaceutics, KLE University’s College of Pharmacy,

Bangalore for their generous consideration and facilities that lead to successful

completion of my project.

To the non-teaching staff: Mr. Biradar, Mr. Suresh, Mr. Satish, Mr.

Reddy for their help and support.

I would like to express my sincere thanks and heartful gratitude to my

batchmates and friends Gopal, Sudheer, Kiran, Ankith, Nirbhay, Pradeep,

Shankar, Melvin Naresh, jagadish, Swathi, Anusha, Nazia, Sanchita,

Haritha, Uma, & Sruthi.

From the core of my heart, I express my special thanks to my friends

from other departments Sundeep, Subrahmanyam, Gopal, Nikhil, Bhargav,

Narendra, Swetha, Amrutha, Rohitha, Roopa and all others.

I would also like to thank my dynamic seniors Ayush, Naveen, Rahul,

Jaydeep, Amol, Jakson, Pradip, Srikant S, Narendra, Vamshi, Nagmanohar,

Anil, Khushboo, Shruthi, Usha , Mounika and Aparna and all others for their

kind co-operation during my research work. I am also thankful to all my juniors

for their support and kind co-operation.

I shall forever remain indebted to my Co-guide S. Godwin Kumar,

Scientist-I, APL Reasearch Centre, Aurobindo Pharma LTD, Hyderabad, allowing

me to carry out M.Pharm dissertation work within a well-established

organization along with their valuable guidance, keen interest, perennial

inspiration and everlasting encouragement. And my thanks to Mr. G.

Ravindranath, V. Sandeep Kumar, Subrahmanyam, Rahul, Anil, Arjun for

their valuable help and guidance during my research work.

Last…….but not the least, I wish to express my gratitude towards “God-

almighty”, who gave me the strength and courage to fulfill my dream and has

showered upon me his choicest blessings.

Thankful I ever remain………

V V GANESH P

IN MEMORY OF MY

D A D

You are my inspiration

ur son…

LIST OF ABBREVIATIONS

API Active Pharmaceutical Ingredient

BBB Blood-Brain Barrier

CNS Central Nervous System

DDS Drug Delivery System

DR Delayed Release

% DR % Drug Release

EC Ethyl Celluose

ER Extended Release

EEG Electroencephalogram

GABA Gamma Aminobutyric Acid

GAD Glutamic Acid Decarboxylase

GAT-1 Gamma Aminobutyric Acid Transporter

HDPE High Density Polyethene

HPC Hydroxy Propyl Celluose

HPMC Hydroxy Propyl Methyl Celluose

HEC Hydroxy Ethyl Celluose

ICH International Conference of Harmonization

LDPE Low Density Polyethene

LOD Loss on Drying

NMDA N-Methyl D-Aspartate

SDS Sodium Dodecyl Sulphate

UV Ultra Violet

USP United States Pharmacoepia

TABLE OF CONTENTS

S.NO CONTENTS Pg NO.

1 ABSTRACT 1

2 INTRODUCTION 2

3 REVIEW OF LITERATURE 17

4 AIM AND OBJECTIVE 18

5 MATERIALS AND METHODS 19

6 RESULTS 33

7 DISCUSSION 53

8 CONCLUSION 56

9 SUMMARY 57

10 BIBLIOGRAPHY 59

LIST OF TABLES

Table No. Table

1.1 Physico-chemical properties of Divalproex Sodium

4.1 List of Materials used in Study

4.2 List of Equipments used in Study

4.3 Limits of Carr’s Index

4.4 Limits of Hausner’s Ratio

4.5 Limits of Angle of Repose

4.6 Drug:Excipient Ratio for Compatibility Study

4.7 Parameters for Tablet Compression

4.8 Formulations for F1-F8

4.9 Dissolution at Acid Stage

4.10 Dissolution at Buffer Stage

5.1 Data for Calibration Curve of Divalproex Sodium

5.2 Physico-Chemical Properties of Innovator Product

5.3 In vitro Drug Release Profile of Innovator Product

5.4 API Characterization

5.5 Drug: Excipient Ratio for Physical Compatibility Study

5.6 Drug: Excipient Ratio for Chemical Compatibility Study

5.7 Evaluation of F1

5.8 In vitro Dissolution Data of F1















5.23 Accelerated Stability Data of F8

LIST OF FIGURES

Figure No. Figure

1.1 Types of Modified Release Tablet

1.2 Drug Release in Swellable Matrix System

1.3 Zones in Swellable Matrix System

1.4 Chemical Structure of Valproic acid

1.5 Chemical Structure of Divalproex Sodium

4.1 Innovator Brand Label

4.2 Schematic Representation of Manfacturing Process

5.1 Standard Graph of Divalproex Sodium

5.2 Innovator Drug Release Profile

5.3 X-Ray Powder Diffraction Study of Divalproex Sodium & Excipients

5.4 Comparative In vitro Drug Release Profile of F1 with Innovator








DIVALPROEX SODIUM ER ABSTRACT

1

DIVALPROEX SODIUM ER Page 1

FORMULATION DEVOLOPMENT AND EVALUATION OF

DIVALPROEX SODIUM EXTENDED RELEASE TABLET

ABSTRACT

The objective of present work is to develop a stable solid dosage form of extended

release tablets of divalproex sodium for the treatment of epilepsy, migraine, and bipolar

disorders. In present study divalproex sodium extended release tablets were prepared using

HPMC as polymer and eudragit NE 40D acts as binding agent and were prepared by wet

granulation technique. This formulation is a hydrophilic matrix formulation, where the drug

is released by diffusion and erosion. This formulation is likely to minimise the variation

between peak and trough plasma levels of valproate over a 24hr dosing period which follows

a zero-order release pattern thus producing essentially flat levels of valproate. This results in

significantly lower the incidence of side effects. This formulation is swelling controlled drug

release system in which drug is released by both diffusion and erosion.

In the preformulation study, the pure drug was evaluated for properties such as bulk

density, tapped density, Compressibility index and Hausner’s ratio. The results indicated that

the drug has poor flow property but passable (Compressibility index = 22.472% and

Hausner’s ratio = 1.292%).The drug excipient compatibility studies indicated that there was

no physical change in the drug when mixed with various excipients and subjected to

accelerated stress conditions (400C/75%RH) upto 4weeks.

Formulations F1 - F8 were prepared by wet granulation technique and each

formulation is evaluated for drug release in comparison to innovator. In formulation F8 the

concentration of starch 1500 was increased to 5.65% and the drug concentration was kept to

53.27% all other concentration were kept same as that of F4. Initially high drug concentration

was observed but maintained all over the time period. The percentage drug release for this

formulation was maintained with innovator in close range. Hence, formulation F8 was

considered to be the optimized formulation in which the release profile was found to be

very close to that of innovator (%DR= 98).

DIVALPROEX SODIUM ER INTRODUCTION

2


1. INTRODUCTION

1.1EPILEPSY:

Epilepsies are a group of disorders of CNS characterized by paroxysmal cerebral

dysrhythmia, manifesting as brief episodes (Seizures) of loss or disturbance of consciousness,

with or without characteristic body movements (Convulsions) 1

. Epileptic seizures result from

abnormal, excessive or hyper synchronous neuronal activity in the brain2. About 50 million

people worldwide have epilepsy, and nearly 80% of epilepsy occurs in developing

countries3. Epilepsy becomes more common as people age

4, 5. Epilepsy is usually controlled,

but not cured, with medication. However, more than 30% of people with epilepsy do not have

seizure control even with the best available medications. Surgery may be considered in

difficult cases. Not all epilepsy syndromes are life long – some forms are confined to

particular stages of childhood. Epilepsy should not be understood as a single disorder, but

rather as syndrome with vastly divergent symptoms, all involving episodic abnormal

electrical activity in the brain and numerous seizures6, 7

.

1.1.1Causes:

The diagnosis of epilepsy usually requires that the seizures (rapid and uncontrolled

body movements due to sudden abnormal and excessive neuronal activity in brain) occur

spontaneously. Nevertheless, certain epilepsy syndromes require particular precipitants or

triggers for seizures to occur. These are termed reflex epilepsy. For example, patients with

primary reading epilepsy have seizures triggered by reading. Photosensitive epilepsy can be

limited to seizures triggered by flashing lights. Other precipitants can trigger an epileptic

seizure in patients who otherwise would be susceptible to spontaneous seizures. For example,

children with childhood absence epilepsy may be susceptible to hyperventilation. In fact,

flashing lights and hyperventilation are activating procedures used in clinical EEG to help

trigger seizures to aid diagnosis. Emotional stress, sleep deprivation, sleep itself, heat stress,

alcohol and febrile illness are examples of precipitants cited by patients with epilepsy.

Notably, the influence of various precipitants varies with the epilepsy syndrome8. Likewise,

the menstrual cycle in women with epilepsy can influence patterns of seizure recurrence.

Catamenial epilepsy is the term denoting seizures linked to the menstrual cycle9.

When investigating the causes of seizures, it is important to understand physiological

conditions that may predispose the individual to a seizure occurrence. Several clinical and

http://en.wikipedia.org/wiki/Neural_oscillation

http://en.wikipedia.org/wiki/Developing_country

http://en.wikipedia.org/wiki/Developing_country

http://en.wikipedia.org/wiki/Surgery

http://en.wikipedia.org/wiki/Hyperventilation

http://en.wikipedia.org/wiki/EEG

http://en.wikipedia.org/wiki/Menstrual_cycle


3


experimental data have implicated the failure of blood–brain barrier (BBB) function in

triggering chronic or acute seizures, some studies implicate the interactions between a

common blood protein albumin and astrocytes10, 11

. These findings suggest that acute seizures

are a predictable consequence of disruption of the BBB by either artificial or inflammatory

mechanisms. In addition, expression of drug resistance molecules and transporters at the BBB

are a significant mechanism of resistance to commonly used anti-epileptic drugs12

.

1.2 TYPES OF EPILEPSY: 1, 13

The clinical classification of epilepsy defines two major categories, namely partial

and generalised seizures.

1.2.1 Generalised Seizures:

Generalised seizures involve the whole brain, including the reticular system, thus

producing abnormal electrical activity throughout both hemispheres. Immediate loss of

consciousness is characteristic of generalised seizures.

TONIC-CLONIC SEIZURES:

It is also called grand mal epilepsy. It is most common and lasts for 1-2 min. It

consists of an initial strong contraction of whole musculature, causing a rigid extensor spasm

and an involuntary cry. Respiration stops and defecation and salvation often occur. The

patient stays unconscious for few more minutes and then gradually recovers.

ABSENCE SEIZURES:

It is also called petit mal epilepsy or minor epilepsy. Absence seizures occur in

children and lasts about 1/2min. They are much less dramatic but may occur more frequently

than grand mal seizures. The patient abruptly ceases whatever he or she is doing and stares

vacantly for few seconds, with little or no motor disturbance. Patients are unaware of their

surroundings and recover abruptly with no after-effects.

ATONIC SEIZURES:

It is also called as akinetic epilepsy. Unconsciousness with relaxation of all muscles

due to excessive inhibitory discharges. Patient may fall.


4


MYOCLONIC SEIZURES:

Momentary contractions of a muscle of a limb or whole body.

INFANTILE SPASMS (HYPSARRHYTHMIA):

Seen in infants. Probably not a form of epilepsy. Intermittent muscle spasm and

progressive mental deterioration. Diffuse changes in the interseizure EEG are noted.

1.2.2Partial seizures:

Partial seizures are those in which the discharge begins locally and often remains

localised. The symptoms depend on the brain region or the regions involved, and include

involuntary muscle contractions, abnormal sensory experiences or autonomic discharge, or

effects on mood and behaviour, often termed psychomotor epilepsy.

SIMPLE PARTIAL SEIZURES:

Lasts for 1 min. Often secondary. Convulsions are confined to a group of muscles or

localised sensory disturbance depending on the area of cortex involved in the seizure, without

loss of consciousness.

COMPLEX PARTIAL SEIZURES:

Attacks of bizarre and confused behaviour and purposeless movements, emotional

changes lasting 1-2 min along with impairment of consciousness. An aura often precedes.

The seizure focus is located in the temporal lobe.

1.3DRUG DELIVERY SYSTEM 14,15,16,17,18

The treatment of acute diseases or chronic illness has been achieved by delivery of

drugs to the patients for many years. These drug delivery systems include tablets, injectables,

suspensions, creams, ointments, liquids and aerosols. Today these conventional drug delivery

systems are widely used. The term drug delivery can be defined as techniques that are used

to get the therapeutic agents inside the human body. Another role of the delivery systems is to

allow the safe application of the drug. This includes that the drug in the formulation must be

chemically, physically and microbiologically stable. Side-effects of the drug and drug

interactions should be avoided or minimized by the use of suitable drug delivery systems.

The delivery systems also need to improve the patient’s compliance with the

pharmacotherapy by the development of convenient applications. For example, one can


5


improve patient compliance by developing an oral dosage form where previously only

parenteral application was possible. Finally, the delivery system needs to be reliable and its

formulation needs to be technically feasible. This means the Pharmaceutical quality of the

delivery systems needs to be assured, drug release from the system needs to be reproducible

and the influence of the body on drug release should be minimized. (For example, food

effects after oral administration).

1.3.1 Conventional Drug Therapy 19,20,21,22

Conventional drug therapy requires periodic doses of therapeutic agents. These agents

are formulated to produce maximum stability, activity and bioavailability. For most drugs,

conventional drug delivery is effective, but some drugs which possess narrow therapeutic

window and which cause irritation to gastric mucosa require modified drug delivery system

to achieve desired therapeutic effect. These delivery systems have a number of advantages

over traditional systems such as improved efficiency, reduced toxicity and improved patient

convenience. The main goal of modified drug delivery systems is to improve the

effectiveness of drug therapies.

Conventional dosage forms are rapidly absorbed, with the ascending and descending

portions of the concentrations versus time curve reflecting primarily the rate of absorption

and elimination, respectively. Because of the rapid rate of absorption from conventional

dosage forms, drugs are usually administered more than once daily, with the frequency being

dependent on biological half-life (t½) and duration of pharmacological effect. The time of

dosing may also be effected by therapeutic index of a drug.

Disadvantages of Conventional Drug Delivery Systems 23

In conventional oral drug delivery systems, there is little or no control over the release

of the drug and effective concentration at the target site.

The dosing pattern in conventional dosage forms results in constantly changing,

unpredictable and often sub-therapeutic plasma concentrations, leading to marked side

effects in some cases.

Conventional drug delivery system is not suitable for the drugs which cause irritation

to the gastric mucosa.

The rate and extent of absorption of drug from conventional formulations may vary

greatly, depending on the factors such as physicochemical properties of the drug,


6


presence of excipients, various physiological factors such as the presence or absence

of food, pH of the gastrointestinal tract, gastrointestinal motility and so on.

1.3.2 MODIFIED DRUG DELIVERY SYSTEMS 24,25

Dosage forms can be designed to modify the release of the drug over a given time or

after the dosage form reaches the required location. Drug release only occurs sometime after

the administration or for a prolonged period of time or to a specific target in the body.

Modifications in drug release are often desirable to increase the stability, safety and efficacy

of the drug, to improve the therapeutic outcome of the drug treatment and/or to increase

patient compliance and convenience of administration.

Classification:

Modified Release dosage form may be classified as

Extended Release

Controlled Release

Sustained release

Delayed Release

1.3.3 Extended release Oral Drug Delivery Systems:

Extended Release oral DDS allows the drug to be released over prolonged time

periods. By extending the release profile of a drug, the frequency of dosing can be reduced.

Extended release can be achieved using sustained or controlled-release dosage forms.

Fig1.1: Types of Modified Release Tablet

MODIFIED-RELEASE TABLET

EXTENDED-RELEASE TABLET

CONTROLLED SUSTAINED

DELAYED-RELEASE TABLET


7


1.3.3.1 Controlled Release Oral Drug Delivery System:

Controlled Release Dosage form is generally accomplished by attempting to obtain

“zero- order” release from the dosage form which independent of the amount of drug in the

delivery system (i.e., a constant release rate). Oral controlled release system continues to be

the most popular and most widely used amongst all the drug delivery systems, because

pharmaceutical agents can be delivered in a controlled pattern over a long period thereby

increasing therapeutic value of the drug. Oral controlled release formulations are becoming

increasingly popular in the pharmaceutical industry because they improve likelihood of a

patient actually taking the medicine, thereby reducing the side effects and providing an

extended patient protection. Oral controlled drug delivery system can be classified as rate

programmed drug delivery system and stimuli-activated drug delivery system.

Classification of Rate-Controlled Drug Delivery System:-

Based on the techniques of drug delivery the controlled release drug delivery systems can be

classified as follows:

1. Rate programmed drug delivery system: In this drug delivery system, the drug release

has been programmed at specific rate profile.

Dissolution controlled drug delivery system.

o Slow dissolution rate of the drug,

o Slow dissolution rate of the reservoir membrane or matrix.

Diffusion controlled drug delivery system.

o Porous matrix controlled system,

o Porous membrane controlled system.

Erosion controlled drug delivery system.

o Surface erosion,

o Bulk erosion.

Combination of dissolution, diffusion and/or erosion controlled drug delivery system.

o Reservoir system,

o Matrix system,

o Hybrid system.

2. Stimuli-activated drug delivery system: In this drug delivery system, the drug release is

activated by some stimuli like biological, chemical and physical energy supplied externally.


8


Activation by the biological process:

Enzyme activated drug delivery system.

o Urea responsive drug delivery system,

o Glucose responsive drug delivery system.

Antibody interaction activated drug delivery system.

Antigen activated drug delivery system.

Inflammation activated drug delivery system.

Activation by the chemical process:

pH activated drug delivery system.

o pH dependent solubility system,

o pH dependent erosion/degradation system,

o pH dependent swelling system.

Ion activated drug delivery system.

Hydrolysis activated drug delivery system.

Chelation activated drug delivery system.

Activation by the physical process:

Electrically activated drug delivery system.

o Iontophoresis,

o Electroporation

Hydrodynamic pressure activated drug delivery system.

Mechanical force activated drug delivery system.

Magnetically activated drug delivery system.

Photo activated drug delivery system.

Photomechanical waves (Laser) activated drug delivery system.

Phonophoresis/sonophoresis/ultrasound activated drug delivery system.

Thermally activated / Temperature responsive drug delivery system.

Osmotic pressure activated drug delivery system.


9


1.3.3.2 Sustained Release Oral Drug Delivery System:

The term Sustained Release is constantly used to describe a pharmaceutical dosage

form formulated to retard the release of the therapeutic agent such that its appearance in the

systemic circulation is delayed and prolonged and its plasma profile is sustained in duration.

The onset of its pharmacological action is often delayed, on the duration of its therapeutic

effect is sustained.

1.3.4 Delayed Release 26, 27

A Delayed Release dosage form is designed to release the drug at a time other than

promptly after administration. Dosage forms can be designed to modify the release of the

drug over a given time or after the dosage form reaches the required location.

Delayed Release oral dosage forms can control where the drug is released, e.g. when

the dosage form reaches the small intestine (enteric-coated dosage forms) or the colon (colon-

specific dosage forms). Delayed Release systems release a bolus of the drug after a

predetermined time in a predetermined location, i.e. they do not release the drug immediately

after ingestion, for example enteric-coated tablets, pulsatile-release capsules.

The two types of delayed release systems are:

Intestinal Release System

Colonic Release System

Intestinal Release System: A drug may be enteric coated for intestinal release for

several known reasons such as to prevent gastric irritation, prevent destabilization in gastric

pH etc.

Colonic Release System: Drugs are poorly absorbed through colon but may be

delivered to such a site for two reasons

Local action in the treatment of ulcerative colitis.

Systemic absorption of protein and peptide drugs.

The extended release once-a-day formulation is a hydrophilic matrix dosage form.

Drug delivery of current formulation is by the combination of diffusion,

dissolution and erosion.


10


1.4 MATRIX SYSTEM:

Matrix tablets are the most extensively used solid dosage forms. They are prepared by

usually compressing a powder containing a drug or drugs with excipients. The goal of

controlled delivery systems are to reduce the frequency and/or to increase the effectiveness of

the drug localization at the target site, thereby reducing the dose required to provide uniform

drug delivery. The commonly used polymers for controlled release are hydroxy propyl

methyl cellulose (HPMC), hydroxy propyl cellulose (HPC), hydroxyl ethyl cellulose (HEC),

ethyl cellulose (EC), methylcellulose (MC), carboxy methylcellulose (CMC), polyvinyl

pyrrolidone (PVP) and polyethylene glycol (PEG).

These polymers, which swell in aqueous medium, are often used for the preparation

of controlled-release dosage forms. These are highlighted with the presence of a solvent

front, the potential for unlimited swelling, and the combined controlling mechanism of

diffusion and erosion as being the distinguishing feature of HM devices.

Advantages perceived for some hydrophilic matrix systems are:

Simplicity of formulation

High drug loading

Reduction in drug blood level fluctuations

Reduction in dosing frequency

Reduction in adverse side effects and

Reduction in health care costs i.e., economy 28

.

1.4.1 Mechanism of drug release from swellable matrix tablets:

Controlled drug release is based on diffusion through polymers, erosion of polymers

and special polymer characteristics such as osmotic and ion exchange properties. When a

glassy (or dry) polymer comes into contact with water or any other medium with which it is

thermodynamically compatible, the solvent penetrates into the free spaces on the surface

between the macromolecular chains. When enough solvent has entered into the matrix, the

glass transition temperature (Tg) of the polymer drops to the level of the experimental

temperature (which is usually 370C) except for poly (ethy1ene oxide) whose Tg is

approximately 600C. Therefore polymers with a Tg greater than 37

0C in their dry (glassy)

state can be used to prepare swelling controlled-release dosage forms. The presence of

solvent in the glassy polymer causes stresses, which are then accommodated by an increase in


11


the radius of gyration and end-to-end distance of the polymer molecules, i.e., the polymer

chains get solvated. The increase in the radius of gyration of the polymer molecules is seen

macroscopically as "swelling of the matrix". The solvent molecules move into the glassy

polymer matrix with a well-defined front at a particular velocity and simultaneously, the

thickness of the swollen or rubbery region increases with time in the opposite direction. The

time taken for the increase in radius of gyration of the polymer molecules, which is a

relational phenomenon, is a characteristic for that particular polymer/solvent system 29

.

A matrix tablet during swelling is an aggregate mass of water-swollen polymer, drug,

and excipients experiencing various degrees of hydration or solution as illustrated in Figure

1.1. The tablet contains regions with solid content varying from 0 to 100%. In the area near

100% solids, the gel is a wetted mass of powders. As water content of the wetted powder

mass increases, the polymer becomes hydrated and develops into a gel. At the outer most

layers, the polymer is diluted to the point where it no longer has structural integrity and

dissolves or wears away. This complex gelatinous layer controls the release of drugs by two

mechanisms.

1. Water-soluble drugs released by diffusion out of the gel layer.

2. Drugs released by erosion of the gel regardless of drug solubility in the dissolution

media. A water insoluble drug is exposed through erosion.

Fig 1.2: Drug release in swellable matrix system


12


Fig1.3: Zones in swellable matrix system

When drug released from a matrix is controlled by diffusion through the polymeric matrix, its

release kinetics obeys Fick’s 1st & 2

nd laws

30:

J = -D

(Eq. 1.1)

= - D

(Eq. 1.2)

Where J represents the diffusional flux of the drug; D is the diffusion coefficient of

the drug; C is the concentration of the drug; and x the distance of diffusion.

When drug release is dominated by surface erosion Korsmeyer and peppas developed

a general model for drug release from a planar matrix containing dissolved drug.

= Kt

n (Eq. 1.3)

log

= logk + n log t (Eq. 1.4).


13


1.5 DRUG PROFILE:

1.5.1 DIVALPROEX SODIUM

Divalproex sodium (DVP) is an anticonvulsant that contains valproic acid and sodium

valproate in a one to-one molar ratio. This medication has recently been shown to be effective

in treatment of acute mania31

and depression32

, suggesting that, like lithium, it has antimanic

and antidepressant properties

Fig 1.4: Chemical Structure of Valproic acid

.

Fig 1.5: Chemical Structure of Divalproex Sodium


14


Table no 1.1: Physico – Chemical Properties of Divalproex Sodium

1.5.2 Site and Mode of Action:33, 34, 35

Divalproex Sodium is active against both pentylenetetrazol and maximal electroshock

seizures. Divalproex Sodium blocks sustained high-frequency repetitive firing of neurons in

culture at therapeutically relevant concentrations. Its action against partial seizures may be a

consequence of this effect on Na+ currents. Blockade of NMDA receptor-mediated excitation

may also be important. Much attention has been paid to the effects of Divalproex Sodium on

GABA. Several studies have shown increased levels of GABA in the brain after

administration of Divalproex Sodium, although the mechanism for this increase remains

unclear. An effect of Divalproex Sodium to facilitate glutamic acid decarboxylase (GAD), the

enzyme responsible for GABA synthesis, has been described. An inhibitory effect on the

GABA transporter GAT-1 may contribute. At very high concentrations, Divalproex Sodium

inhibits GABA-T in the brain, thus blocking degradation of GABA. However, at the

relatively low doses of Divalproex Sodium needed to abolish pentylenetetrazol seizures, brain

GABA levels may remain unchanged. Divalproex Sodium produces a reduction in the

aspartate content of rodent brain, but the relevance of this effect to its anticonvulsant action is

not known. At high concentrations, Divalproex Sodium has been shown to increase

membrane potassium conductance. Furthermore, low concentrations of Divalproex Sodium

Description White or almost white crystalline powder

Chemical name compounded from sodium valporate and

valporic acid in 1:1 ratio

Molecular formula C8H16O2C8H15O2Na

Molecular weight 310.41

Solubility Soluble in Ethanol (95%), Methanol, IPA, Partially

soluble in water and ether

Melting Point 222 °C

Functional category Mania, Epilepsy (Complex partial, simple and

complex petit mal), Migraine

Pharmacopoeial status USP

Storage conditions Store in air tight containers, Protect from light, at a

temperature between 20C and 8

oC


15


tend to hyperpolarize membrane potentials. These findings have led to speculation that

Divalproex Sodium may exert an action through a direct effect on the potassium channels of

the membrane.

Divalproex Sodium probably owes its broad spectrum of action to more than one molecular

mechanism.

1.5.3 Pharmacokinetics:34,35

Absorption and distribution:

Valproate is well absorbed following an oral dose, with bioavailability greater than

80%. Peak blood levels are observed within 2 hours. Food may delay absorption, and

decreased toxicity may result if the drug is given after meals.

Valproic acid is 90% bound to plasma proteins, although the fraction bound is

somewhat reduced at blood levels greater than 150 g/mL Since valproate is both highly

ionized and highly protein bound, its distribution is essentially confined to extracellular

water, with a volume of distribution of approximately 0.15 L/kg.

Metabolism and excretion:

Sodium valproate is extensively metabolised in the liver and has a t1/2

of 13 hrs. It is

90% bound to plasma albumin. Sodium valproate is a nonspecific inhibitor of metabolism,

and indeed inhibits its own metabolism. Sodium valproate does not induce drug metabolising

enzymes but its metabolism is enhanced by induction due to other drugs, including

antiepileptics

Clearance for valproate is low; its half-life varies from 9 hours to 18 hours. At very high

blood levels, the clearance of valproate is dose-dependent. There appear to be offsetting

changes in the intrinsic clearance and protein binding at higher doses. Approximately 20% of

the drug is excreted as a direct conjugate of valproate.

Drug Interactions

As noted above, the clearance of valproate is dose-dependent, caused by changes in

both the intrinsic clearance and protein binding. Valproate inhibits its own metabolism at low

doses, thus decreasing intrinsic clearance. At higher doses, there is an increased free fraction

of valproate, resulting in lower total drug levels than expected. It may be clinically useful,


16


therefore, to measure both total and free drug levels. Valproate also displaces phenytoin from

plasma proteins. In addition to binding interactions, valproate inhibits the metabolism of

several drugs, including phenobarbital, phenytoin, and carbamazepine, leading to higher

steady-state concentrations of these agents. The side effects and toxicity of phenytoin are

enhanced. The inhibition of phenobarbital metabolism may cause levels of the barbiturate to

rise precipitously, causing stupor or coma.

DIVALPROEX SODIUM ER LITERATURE REVIEW

17


2. REVIEW OF LITERATURE

Emilio perucca, repoted a detailed introduction to anti-epileptic drugs giving the

mechanism of action of each class of anti-epileptic drugs, explaining the efficacy spectrum,

clinical pharmacokinetics and therapeutic drug monitoring for each class. The paper also

focused on adverse effect profile and drug interaction. Concluding that anti-epileptic drugs

differs from other in terms of pharmacological properties, efficacy spectrum, side effect

profile, interaction potential and cost.36

Kumar et al proposed oral extended release drug delivery system as a promising

approach, stating the suitable candidate for extended release drug delivery system along with

merits and demerits of extended release drug delivery system. They briefly explained the

factors affecting the release from extended release drug delivery system, different polymers

used with their classification. They concluded that the extended release formulations are

known to increase the effectiveness of drugs with short half-life and also improve patient

compliance by reducing the dosing frequency.37

Manivannan et al developed an extended release once a day formulation of divalproex

sodium using direct compression method. The direct compression technique using the rate

controlling polymers like HPMC K100M, HPMC K4M was found to could produce a stable

product.38

Arunachalam et al developed an extended release once a day formulation of

divalproex sodium using direct compression the results obtained were found to be within the

specification limits and the optimized batch was found to be stable showing zero order

release kinetics.39

Fagiolino et al reported the actual bioavailability of divalproex sodium extended

release tablet. The absolute oral bioavailability of divalproex sodium is 89% though the oral

absorption of the drug was practically 100%. They also stated different formulas to calculate

the ratio of drug absorption for divalproex sodium ER and DR tablets.40

Jeganath et al worked on the stability of divalproex sodium ER tablets prepared by

direct compression. The physical and chemical properties of the tablets were assessed during

three months (accelerated stability). The Divalproex sodium tablet prepared by direct

compression were stable with good in vitro drug release.41

DIVALPROEX SODIUMER AIM AND OBJECTIVE

18


3. AIM AND OBJECTIVE

The primary objective of the study was to formulate an extended release tablet of

DIVALPROEX SODIUM that is likely to have fewer side effects. The tablet developed may

maintain effective plasma concentration of drug over a 24 hour dosing period and thus

improve patient compliance.

The specific objectives to be achieved include:

1) To formulate an extended release dosage form.

2) To formulate a dosage form that will permit once-a-day dosing.

3) To evaluate the prepared extended release tablets.

4) To perform the stability studies.

DIVALPROEX SODIUM ER MATERIALS & METHODS

19


4. MATERIALS AND METHODS

4.1 Materials used for the study:

Table 4.1: List of materials used in the study

S.No Material Manufacturer

Intra granular ingredients

1 Divalproex Sodium Katwijk Chmie bv

2 Hypromellose USP (Benecel 874) Aqualon

3 Pregatinized Starch USNF (Starch 1500) Colorcon

4 Mannitol USP (Mannitol 35) Roquette

Binder Ingredients

5 Polyacrylate Dispersion 40 Percent (Eudragit NE 40

D) Evonik Industries

6 Purified Water

Extra Granular Ingredients

7 Silicified Microcrystalline Celluose (Prosolv SMCC

50) JRS Pharma

8 Silicon Dioxide USNF (Syloid 244 FP) Grace Davision

Film Coating

9 Opadry II Grey 41L57504 Colorcon


20


4.2 Equipments used in the study:

Table 4.2: List Equipments used in the study

S.No Equipment Manufacturer Model No.

1 Electronic Balance Sartorius, Germany BT 2233

2 Tap density tester Electrolab, Mumbai ET 1020

3 Electromagnetic Sieve

shaker Restech, New Delhi AS 200

4 Double cone blender Rimek, Ahmedabad KALWEKA HD 410 AC

5 Laboratory Stirrer Remi, Mumbai RQT 124 A

6 Rotor Mixer Granulator Gansons, Mumbai HSMG

7 Rapid air Dryer Restech, New Delhi TG 100

8 Loss on Drying Machine Sartorius, Germany MA 100

9 Multimill Grovers International Lab scale multi mill 116

10 Comill Quadro, Canada U5-0280

11 Compression Machine 20

station Cadmach, Ahmedabad CMD 4

12 Hardness tester Varian, Carolina, US VK 200

13 Friabilator Electrolab, Mumbai EF 2

14 Vernier Caliper Multiyoyo Japan

15 Coating Machine Gansons, Mumbai GAC 250/375

16 Peristaltic Pump Electrolab, Mumbai PP 210 V

17 Dissolution tester Type II

USP Electrolab, Mumbai TDT 08L

18 pH tester Eutech Instruments,

Singapore pH 1500

19 Magnetic stirrer Deepali Magnetic

Stirrer, Mumbai MS 1


21


4.3 CALIBRATION CURVE OF DIVALPROEX SODIUM BY UV SPECTRO

PHOTOMETRIC METHOD:

Standard curve for Divalproex Sodium with 0.05M Phosphate buffer with 75mM SDS,

pH 5.5:

To prepare standard solution of solvent/buffer 21.6g of sodium dodecyl sulphate/SDS,

6.9g of sodium dihydrogen phosphate monohydrate, and 0.12g of sodium hydroxide were

dissolved in 1l of water and pH was adjusted to 5.5. 50mg of Divalproex Sodium was

weighed and transferred into 50ml volumetric flask and volume was made up using the

buffer. About 1ml of the above solution was transferred to 10ml volumetric flask and volume

was made up with standard buffer solution. Aliquots of 0.2 ml, 0.4 ml, 0.6 ml, 0.8 ml, 1 ml

were pipetted out from stock solution and diluted to 10 ml with standard buffer solution to

give standard solutions having concentrations of 2mcg/ml, 4mcg/ml, 6mcg/ml, 8mcg/ml and

10mcg/ml. The absorbance of the solutions was determined at 210nm against standard buffer

solution as the blank. The standard curve of divalproex sodium was obtained by plotting

absorbance on Y-axis against concentration on X-axis.

4.4 INNOVATOR PRODUCT DETAILS: The objective of the present work was to match the release characteristics of the

developed tablets with that of innovator product (DEPAKOTE®

ER 500-Abott Pharmaceuticals

PR LTD). The innovator product was evaluated for physical properties, drug content and in-

vitro drug release to set a target for the product to be developed.

Fig 4.1: Innovator (DEPALOTE ER Abott Pharmaceuticals PR LTD) Brand Label


22


4.5 PREFORMULATION STUDIES: Preformulation can be defined as investigation of physical and chemical properties of

drug substance alone and when combined with excipients. Preformulation studies are the first

step in the rational development of dosage form of a drug substance. The objectives of

Preformulation studies are to develop a portfolio of information about the drug substance,

which helps in formulation development. The drug was evaluated for the following

parameters during Preformulation studies:

4.5.1 Bulk Density (BD):

Twenty five grams of drug which was previously passed through #20 sieve was

accurately weighed and transferred in 100 ml graduated cylinder. The powder was carefully

levelled without compacting, and the unsettled apparent volume was read. The apparent bulk

density in g/ml was calculated by the following formula;

Bulk density = Weight of powder / Bulk volume …………….. eq.1

4.5.2 Tapped bulk density (TD):

Twenty five grams of drug which was previously passed through #20 sieve was

weighed accurately then transferred in 100 ml graduated cylinder. The cylinder containing

the sample was mechanically tapped by raising the cylinder and allowed to drop under its

own weight using mechanically tapped density tester that provides a fixed drop of 14±2 mm

at a nominal rate of 250 drops per minute. The cylinder was tapped for 250 times initially and

the tapped volume (V1) was measured to the nearest graduated units, the tapping was

repeated for an additional 750 times and the tapped volume (V2) was measured to the nearest

graduated units. If the difference between the two volumes is less than 2% then final the

volume (V2), the tapped bulk density in g/ml was calculated by the following formula:

Tapped Density = Weight of powder / Tapped volume………………eq.2


23


4.5.3 Carr’s index:

The compressibility of powder was determined by Carr’s compressibility index.

Carr’s Index (%) = [(TD-BD) x100]/TD …………… eq. 3

Table No: 4.3 Limits for Carr’s Index

Excellent <10

Good 11 – 15

Fair 16 – 20

Passable 21 – 25

Poor 26 – 31

Very poor 32 – 37

Very very poor >38

4.5.4 Hausner’s ratio:

Hausner’s ratio was determined by using the following equation.

Hausner’s Ratio = TD / BD …………………….eq.4

Table No: 4.4 Limits for Hausner’s Ratio

Excellent 1.00 – 1.11

Good 1.12 – 1.18

Fair 1.19 – 1.25

Passable 1.26 -1.34

Very poor 1.35 -1.45

Very very poor >1.60


24


4.5.5 Angle of repose:

The angle of repose of drug was determined by the funnel method. The accurately

weighed powder blend was taken in the funnel. The height of the funnel was adjusted in such

a way that the tip of the funnel just touched the apex of the powder blend. The powder blend

was allowed to flow through the funnel freely on to the surface. The diameter of the powder

cone was measured and angle of repose was calculated using the following equation.

Tan Ɵ = h/r ……………..eq.5

Where, h and r were the height and radius of the powder cone respectively.

Table No: 4.5 Effect of angle of repose on flow property

Angle of Repose (Ɵ) Type of Flow

< 20 Excellent

20-30 Good

30-34 Passable

>35 Very poor

4.6 COMPATIBILITY STUDIES:

The objective of the study was to assess the compatibility of Divalproex Sodium with

excipients used in the formulation. Drug: Excipient blends in the ratios specified in the table

were incubated in clear, molded glass vials closed with LDPE caps at 600C for 15 days and at

400C / 75% RH for a period of one month and observed for change in physical and chemical

attributes.


25


Table No 4.6: Drug: Excipient ratio for compatibility studies

S.no Composition details Drug: excipients

1 Divalproex sodium NA

2 Divalproex sodium + pregelatinized starch(starch 1500) 1:5

3 Divalproex sodium + HPMC (Benecel Mp 874 Pharm) 1:5

4 Divalproex sodium + mannitol 35 1:5

5 Divalproex sodium + polyacrylate dispersion 40 percent

( eudragit NE 40 D) 1:5

6 Divalproex sodium + silicified microcrystalline

cellulose ( Prosolv SMCC 50) 1:5

7 Divalproex sodium + silicon dioxide USNF ( Syloid 244

FPP ) 1:2

8 Divalproex sodium + Opadry II Gray 41L57504 1:1

9 Divalproex sodium + Opadry white 06L58769 1:1

4.7 X-RAY POWDER DIFFRACTION: The initial and three months samples of Divalproex Sodium ER tablets of 40

0C/75%

RH conditions were analysed by X-ray powder diffraction to evaluate any change in the

polymorphic form of Divalproex Sodium during formulation preparation and subsequent

storage at accelerated stability conditions. The excipients used in the preparation are almost

amorphous in nature and show only few diffraction peaks of weak intensity, which do not

interfere in the polymorphic identity conformation of Divalproex Sodium in the formulation.


26


4.8 MANUFACTURING PROCESS DEVOLOPMENT:

The manufacturing process of Divalproex Sodium Extended Release Tablets is as follows:

4.8.1 SIFTING:

a) Divalproex sodium was passed through multi mill with 1.5 mm screen at low speed

then mannitol 35 was passed for rinsing.

b) The above material (drug + mannitol 35) is sifted through 30# sieve.

c) Hypromellose was sifted through 30 # sieve.

d) Pregelatinised starch was sifted through 30 # sieve.

4.8.2 GRANULATING DISPERSION:

a) Polyacrylate dispersion 40% was passed through 100 # nylon cloth.

4.8.3 DRY MIXING:

a) The sifted material of b,c,d of first step was loaded in RMG.

b) Dry mixed for 10min at slow impellar speed and chopper off.

4.8.4 GRANULATION:

a) Filtered polyacrylate dispersion 40% of step 2 was added to the above dry mix for

over 4 min with slow impellar speed and slow chopper speed.

b) If required extra quantity of purified water (NMT 6%) was added over a period of

30sec with slow impellar speed and slow chopper speed.

c) The wet mass was kneaded for 30sec or more with slow impellar speed and high

chopper speed, till desired mass is obtained.

d) The wet mass was unloaded at slow impellar speed and high chopper speed.

4.8.5 DRYING AND MILLING:

a) The wet mass was airdried in air dryer for 10min followed by drying at an inlet

temperature of 45±50C to get LOD in range of 5-8% w/w at 80

0C in auto-mode

using suitable moisture analyser.


27


b) The semi dried granules were milled using multi mill through 6 mm screen at

medium speed.

c) The milled granules were dried at an inlet temperature of 45±50C in air dryer to get

LOD in range of 3-5% w/w at 800 C in auto-mode using suitable moisture analyser.

d) The dried granules were again multi milled using 1.5 mm screen at medium speed.

e) The milled granules were dried at 60±50 C in air dryer to get LOD not more than

2% w/w at 800 C in auto-mode using suitable moisture analyser.

f) The above granules were sifted through 20 # and the passed granules were collected

in double polybag.

g) The retains were collected and multi milled using 1.5 mm screen at medium to fast

speed.

h) The milled granules were added to the granules from step.F

4.8.6 SIFTING:

a) SMCC was sifted through 40#.

b) Silicon dioxide was sifted through 40#.

4.8.7 BLENDING:

a) The collected granules were loaded into low shear blender.

b) SMCC was added to the above step and blended for 15min.

c) Silicon dioxide was added to the above step and blended for 30min.

d) The lubricated granules were stored in double polyethene lined triple laminated

aluminium bags with desiccant if unloaded from the blender.

4.8.8 BLEND SAMPLE ANALYSIS:

a) Blend sample was sent for analysis.

4.8.9 COMPRESSION:

a) The blend was loaded into the hopper and continued with compression using

suitable compressing machine maintaining the following parameters:


28


Table no 4.7: Parameters for Tablet Compression

Shape White to off white, oval shaped uncoated

tablets with plain surface on both sides.

Tooling 18.8 X 9.7mm oval shaped punches and dies.

Average weight 1010mg ± 2%

(989.8mg-1030.2mg)

Hardness 10-18Kp

Thickness 7.9±0.4mm

(7.5mm-8.3mm)

friability NMT 0.8% w/w

Weight variation ±5% of target weight

4.8.10 FILM COATING DISPERSION / SUSPENSION PREPARATION:

a) Purified water was taken in plastic beaker and stirred with suitable stirrer.

b) Opadry II grey was dispersed into above water while stirring and continued

stirring for 45min.

4.8.11 FILM COATING:

a) The compressed tablets were loaded into perforated coating pan and pre warmed

at inlet temperature of 60±100C with an intermittent inching of coating pan.

b) Spraying of opadry II grey suspension was started at an inlet temperature of

60±100 C when product temperature of 45

0 C was attained.

c) The coating parameters were recorded.

d) Coating was continued to get 2.75-3.25% w/w build up.

e) Spraying was stopped when the required build up percentage was attained and

then the coated tablets were dried for 15min at 60±100C.

f) The tablets were unloaded and continued for packing.


29


Fig 4.2: Schemtic representation of Manufacturing Process

Sifting and Dry Mixing

Wet Granulation

Drying and Milling

Blending

Compression

Film Coating

& Packing

BLENDER

ROTOR MIXER GRANULATOR

MULTI MILL

COMPRESSION

MACHINE


30


Table no. 4.8: Formulations F1-F8

S.No Material

Formulation Code F (mg)

F1 F2 F3 F4 F5 F6 F7 F8

Intra granular ingredients

1 Divalproex Sodium 538.1 538.1 538.1 539.34 538.1 538.1 538.1 538.1

2 Hypromellose USP

(Benecel 874) 161.6 171.7 171.7 171.7 171.7 171.7 171.7 171.7

3 Pregatinized Starch USNF

(Starch 1500) 48.2 38.1 59.60 55.86 59.60 56.20 58 57.1

4 Mannitol USP (Mannitol

35) 120 120 98.2 101 101 101 101 101

Binder Ingredients

5

Polyacrylate Dispersion

40 Percent (Eudragit NE

40 D) 47.1 47.1 47.1 47.1 47.1 47.1 47.1 47.1

6 Purified Water qs qs qs qs qs qs qs qs

Extra Granular Ingredients

7

Silicified Microcrystalline

Celluose (Prosolv SMCC

50) 50 50 50 50 47.5 50 50 50

8 Silicon Dioxide USNF

(Syloid 244 FP) 45 45 45 45 45 45.9 44.1 45

Film Coating

9 Opadry II Grey 41L57504 qs qs qs qs qs qs qs qs


31


4.9 Evaluation of Extended Release Tablets:

Weight variation test

Individual weights of 20 capsules were taken randomly and the average weight was

calculated by using the following formula.

4.10 IN VITRO DISSOLUTION STUDY

Table No: 4.9 Dissolution at acid stage

Parameters Dissolution at acid stage

media

Media 0.1N HCl

Apparatus USP II apparatus (Paddle)

RPM 50

Amount of media 500ml

Time 45min

Temperature 37 ±50C

There is no release of any drug substance during this stage

Table No: 4.10 Dissolution at buffer stage

Parameters Dissolution at Buffer stage

media

Media 0.05M Phosphate buffer with 75mM

SDS, pH 5.5

Apparatus USP II apparatus (Paddle)

RPM 100

Amount of media 900ml

Time 24hrs

Temperature 37 ±50C


32


The absorbance of sample is measured in 1cm cell on suitable UV Spectrophotometer at

210nm, using medium as blank and the absorbance was recorded.

4.11 STABILITY STUDIES:

Stability studies were an integral part of the drug development program and are one of

the most important areas in the registration of pharmaceutical products. The purpose of

stability testing is to provide evidence on how the quality of a drug substance or drug product

varies with time under the influence of a variety of environmental factors such as temperature,

humidity, light and enables recommended storage conditions, re-test periods and self-

half-lives to be established. Degradation products, degradation pathway were determined

by stability assessment pathway. In these types of studies the tablets were stored in

suitable containers or blister packages and stability study is conducted as per ICH guidelines.

The product was analysed at intervals for various parameters which may include assay of

active ingredient, measurement of known disintegration time, dissolution time, appearance,

etc., Stability studies has been conducted at following conditions.

Storage conditions

Accelerated: - 40 ºC ± 2 ºC /75%RH ± 5%RH

As per ICH guidelines, the samples for stability analysis must be exposed to an

environment of 40˚C ± 2˚C / 75%RH ± 5% RH for a period of 6 months. As per the standard

protocol the samples must be analysed at 0, 1, 2, 3 and 6 months’ time points.

Accelerated stability studies were performed for the final optimized formulation (F8).

Samples were analysed at 1, 2, 3 months’ time points.

DIVALPROEX SODIUM ER RESULTS

33


5. EXPERIMENTAL RESULTS

5.1 CALIBRATION CURVE OF DIVALPROEX SODIUM BY UV

SPECTROPHOMETRIC METHOD:

Standard graph of Divalproex Sodium in 0.05M Phosphate buffer with 75mM SDS, pH

5.5 at λmax 210.0 nm

Standard curve of Divalproex Sodium was found to be linear over a concentration range of 2-

10µg/ml with R2

=0.997.

The absorbance values of different concentrations are shown in table 5.1 and standard curve

is shown in the figure 5.1.

Table No 5.1: Data for calibration curve of Divalproex Sodium

Concentration(mg/ml) Absorbance at 210nm

0 0.01

2 0.06

4 0.132

6 0.212

8 0.268

10 0.327


34


Figure 5.1: Standard graph of Divalproex Sodium

5.2 INNOVATOR PRODUCT DETAILS:

Table No 5.2: Physico chemical properties of innovator product DEPAKOTE ER

500mg

Parameters Observation

Description

Grey ovaloid, film coated tablets imprinted with ‘a’ and ‘HC’ on one

side and other side plain

Market USA

Label Claim Each tablet contains Divalproex Sodium equivalent to Valproic acid

500mg

Average

weight(mg) 1039

Coated/ Uncoated Film coated

Length(mm) 19.02

Thickness(mm) 8.11

Water by KF (%) 2.67

0.01

0.07

0.132

0.212

0.268

0.327

y = 0.0323x + 0.0085 R² = 0.9978

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 2 4 6 8 10 12

A

b

s

o

r

b

a

n

c

e

Concentration µg/ml

Standard curve of Divalproex Sodium in 0.05M Phosphate buffer

with 75mM SDS, pH 5.5

Series1


35


Innovator In-vitro Drug Release Profile: In 0.05M Phosphate buffer with 75mM SDS

The in-vitro drug release profile of innovator product is shown in table no. 5.3 &

figure no. 5.2

Table No: 5.3 In-vitro drug release profile of innovator product

TIME(Hr) % DRUG RELEASE

3 21

6 33

9 47

12 60

15 71

18 85

21 92

24 98

Figure 5.2: Innovator Drug Release profile

0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator Drug Release Profile


36


5.3 PREFORMULATION STUDIES:

API CHARECTERIZATION:

APPEARANCE: White or almost white crystalline powder.

SOLUBILITY: The drug is highly soluble in Chloroform, freely soluble in Methanol, and in

Ethyl Ether, Soluble in Acetone, Partially soluble in Acetonitrile

The results of pre formulation studies of API were shown in table 5.4

Table No: 5.4 API Characterization

S. No Characteristics Results

1 Bulk Density (gm/ml) 0.325

2 Tapped Density (gm/ml) 0.420

3 Compressibility index

(%) 22.472

4 Hauser’s ratio 1.292

6 Loss on drying (LOD)

(%) ≤ 2.0

7 max 210 nm


37


5.4 Drug excipient interaction studies: The results of Drug:Excipient compatibility studies were shown in table no 5.5

Physical compatibility:

Table No 5.5: Drug: Excipients Physical compatibility study

S.no Composition

details

Drug:

excipients

Description

initial 60

0C 40

0C/75%RH

15days 1 month

1 Divalproex

sodium NA

White

color

powder

NCC NCC

2

Divalproex

sodium +

pregelatinized

starch(starch

1500)

1:5

White

color

mixture

White to

off white

color

mixture

White to off white

color mixture

3

Divalproex

sodium + HPMC

(Benecel Mp 874

Pharm)

1:5

White to

off white

color

mixture

NCC NCC

4

Divalproex

sodium +

mannitol 35

1:5

White

color

mixture

NCC NCC

5

Divalproex

sodium +

polyacrylate

dispersion 40

percent ( eudragit

NE 40 D)

1:5

White

color

dispersion

Off white

color hard

cake

Off white color

hard cake

6

Divalproex

sodium +

silicified

microcrystalline

cellulose (

Prosolv SMCC

50)

1:5

White to

off white

color

mixture

Off white

to pale

yellow

color

mixture

NCC

7

Divalproex

sodium + silicon

dioxide USNF (

Syloid 244 FPP )

1:2

White

color

mixture

NCC NCC

8

Divalproex

sodium + Opadry

II Gray

41L57504

1:1 Gray color

mixture NCC

NCC

NA = not applicable

NCC = no characteristic change


38


Chemical compatibility: The results of Drug:Excipient compatibility studies were shown in

table no 5.6

Table No 5.6: Drug: Excipients Chemical compatibility study

S.No Composition

details

Drug :

Excipients

Assay ( % )

Initial 600C 400C/75%RH

15days 1 month

1 Divalproex

sodium NA 101.0 100.2 91.2

2

Divalproex

sodium +

pregelatinized

starch(starch

1500)

1:5 101.1 98.8 82.9

3

Divalproex

sodium + HPMC

(Benecel Mp 874

Pharm)

1:5 103.3 100.3 105.5

4

Divalproex

sodium +

mannitol 35

1:5 102.3 100.7 104.4

5

Divalproex

sodium +

polyacrylate

dispersion 40

percent ( eudragit

NE 40 D)

1:5 96.6 * *

6

Divalproex

sodium +

silicified

microcrystalline

cellulose (

Prosolv SMCC

50)

1:5 101.4 99.4 104.0

7

Divalproex

sodium + silicon

dioxide USNF (

Syloid 244 FPP )

1:2 94.0 95.1 103.2

8

Divalproex

sodium + Opadry

II Gray

41L57504

1:1 101.0 96.1 100.2

NA = Not applicable

* = Forms a hard cake which cannot be redispersed and hence accurate analytical results not available


39


5.5 X-RAY Powder diffraction study:

The X-ray powder diffraction pattern of Divalproex sodium extended release tablets exhibits

the diffraction peaks characteristic of Divalproex sodium, thereby indicating no change in the

polymorphic form of divalproex sodium during formulation, preparation as well as during

stability storage period.

An overlay of the X-ray powder diffraction pattern of the following samples is enclosed

herewith:

a) Divalproex sodium API

b) Divalproex sodium Extended release tablets ( initial )

c) Divalproex sodium Extended release tablets ( after storage at 400C / 75% RH for a

period of 3months)

d) Placebo

Fig 5.3: X-Ray Powder Diffraction Study of Divalproex Sodium with Excipients


40


5.6 FORMULATION DIVALPROEX SODIUM EXTEDED RELEASE

TABLETS

The extended release matrix formulation of divalproex sodium was achieved by wet

granulation method.

EVALUATION OF DIVALPROEX SODIUM EXTENDED RELEASE TABLETS

Table No 5.7: Evaluation of F1:

Parameters Values

DRY MIX

Bulk density (g/ml) 0.309

LUBRICATED BLEND


Tapped density (g/ml) 0.589

Compressibility index ( % ) 20.515

Hausner’s ratio 1.17

CORE TABLET

Hardness ( KP ) 12.1

Thickness ( mm ) 8.23

Friability ( % m/m ) Nil

Average weight ( mg ) 1011.2

Weight variation ( mg ) 1008-1013

FILM COATED TABLET

Weight ( mg ) 1035



Table No: 5.8: In-vitro dissolution Data of F1:

Acid stage

S.No: Time (hrs) % Drug release

1 45Min 0

Buffer stage

1 3 20

2 6 32

3 9 45

4 12 54

5 15 63

6 18 75

7 21 82

8 24 88


41


Figure 5.4: Comparative Invitro drug release profile of F1 with Innovator


Parameters Values

DRY MIX


LUBRICATED BLEND





CORE TABLET






FILM COATED TABLET

Weight ( mg ) 1042



0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator

F1


42


Table No 5.10: In-vitro dissolution Data of F2:

Acid stage


1 45Min 0

Buffer stage

1 3 21

2 6 32

3 9 43

4 12 51

5 15 65

6 18 73

7 21 86

8 24 90


0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator

F2


43


Table No5.11: Evaluation of F3:

Parameters Values

DRY MIX


LUBRICATED BLEND





CORE TABLET






FILM COATED TABLET

Weight ( mg ) 1037.5




Acid stage


1 45Min 0

Buffer stage

1 3 20

2 6 36

3 9 45

4 12 54

5 15 69

6 18 77

7 21 85

8 24 92


44




Parameters Values

DRY MIX


LUBRICATED BLEND





CORE TABLET






FILM COATED TABLET

Weight ( mg ) 1042



0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator

F3


45



Acid stage


1 45Min 0

Buffer stage

1 3 22

2 6 40

3 9 53

4 12 60

5 15 69

6 18 80

7 21 85

8 24 92


0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator

F4


46



Parameters Values

DRY MIX


LUBRICATED BLEND





CORE TABLET






FILM COATED TABLET





Acid stage


1 45Min 0

Buffer stage

1 3 22

2 6 40

3 9 53

4 12 60

5 15 69

6 18 80

7 21 85

8 24 92


47



Table No 5.17 Evaluation of F6:

Parameters Values

DRY MIX


LUBRICATED BLEND





CORE TABLET






FILM COATED TABLET




0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator

F5


48



Acid stage


1 45Min 0

Buffer stage

1 3 23

2 6 42

3 9 50

4 12 59

5 15 68

6 18 75

7 21 85

8 24 94


0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator

F6


49


Table No 5.19 Evaluation of F7:

Parameters Values

DRY MIX


LUBRICATED BLEND





CORE TABLET






FILM COATED TABLET

Weight ( mg ) 1039




Acid stage


1 45Min 0

Buffer stage

1 3 24

2 6 42

3 9 51

4 12 59

5 15 69

6 18 77

7 21 88

8 24 95


50




Parameters Values

DRY MIX


LUBRICATED BLEND





CORE TABLET






FILM COATED TABLET

Weight ( mg ) 1049



0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator

F7


51


Table No 5.22 In-vitro dissolution Data of F8:

Acid stage


1 45Min 0

Buffer stage

1 3 25

2 6 44

3 9 53

4 12 63

5 15 79

6 18 85

7 21 92

8 24 99


0

20

40

60

80

100

120

0 5 10 15 20 25 30

Innovator

F8


52


5.7 ACCELERATED STABILITY DATA OF FORMULATION (F8):

Table No 5.23 Accelerated Stability Data of F8:

Product Name Divalproex Sodium ER 500mg Tablets (F8)

Packing HDPE Heavy weight container with 1g Silica gel (100’s count)

Condition 400C/75%RH

Period Initial 1M 2M 3M

Assay (%) 100.7 99.2 98.6 98.9

Appearance

White to off

white color

mixture

NCC NCC NCC

Dissolution % Drug Released

3 21 22 21 23

6 37 38 35 39

9 50 51 49 50

12 61 62 57 59

15 72 71 66 69

18 82 78 75 76

21 89 85 84 85

24 97 92 90 93

DIVALPROEX SODIUM ER DISCUSSION

53


6. DISCUSSION

The present work aims to formulate extended release matrix tablets of Divalproex

sodium with a view to reduce the incidence of side effects associated with conventional

tablets and reduce the frequency of drug administration thereby to improve patient

compliance.

The calibration curve of Divalproex sodium was constructed by UV-

spectrophotometer. It was found that the curve was linear over a concentration range of 2-10

μg/ml with r2 value of 0.997.




Hausner’s ratio = 1.292%).

The drug excipient compatibility studies indicated that there was no physical change

in the drug when mixed with various excipients and subjected to accelerated stress conditions

(400C/75%RH) upto 4weeks.

X-Ray diffraction studies of the drug and excipients indicated that the characteristic

peaks of the drug were retained in the mixture there by indicating absence of interaction

between the drug and the excipients.

The intention of present work was to develop a product having release profile similar

to the innovator product. Hence the innovator product (DEPAKOTE®ER) was evaluated to

determine the characteristics of final product. Based on the percentage drug release of the

innovator product, the target release was calculated.

In formulation F1 polymer concentration was 16%, drug concentration was 53.27%.

Initially the drug release was same as that of innovator but to the end it failed to maintain the

drug release as that of innovator. This may be due to the low polymer concentration drug

release rate was not maintained.


54


In formulation F2 polymer concentration was increased to 17% by decreasing the

diluent concentration (strach1500) to 3.77%. The formulation failed to achieve the innovator

drug release this may be due to increased polymer concentration.

In formulation F3 polymer concentration was kept same as that of F2 and diluent

concentrations were altered, concentration of strach1500 was increased to 5.90% and

concentration of mannitol35 was decreased to 9.7%. In this formulation drug release was not

constant, however it does not reached innovator concentration. This may be due to the

increased concentration of starch 1500.

In formulation F4 drug concentration was increased to 53.4% by lowering the

concentration of starch1500 to 5.53%. And mannitol was increased to 10%. Initially the drug

release was high but slowly it came down. The drug release was not linear. Increased drug

concentration did not help.

In formulation F5 the concentration of prosolv SMCC 50 was lowered to 4.7% and

the concentration of starch1500 was increased 5.90%. The drug release was not linear same

as that of F4.

In formulation F6 the concentration of syloid 244 FP (silicon dioxide) was increased

to 4.54%, decreasing the starch 1500 concentration to 5.56%. Initially rapid drug release was

observed and then the drug concentration came down.

In formulation F7 syloid 244 FP concentration was reduced to 4.37% and starch 1500

concentration was increased to 5.74% the drug release same as that of F6.

In formulation F8 the concentration of starch1500 was decreased to 5.65% and the

drug concentration was kept to 53.27% all other concentration were kept same as that of F4.

Initially high drug concentration was observed but maintained all over the time period. The

percentage drug release for this formulation was maintained with innovator in close range.

Hence, formulation F8 was considered to be the optimized formulation based on

the values obtained from F4-F7 the increased concentrations of starch in the formulation

is affecting the drug release. The release profile of F8 was found to be very close to that

of innovator (%DR= 98).

The optimized final formulation was packed in HDPE heavy weight container with 1g

silica gel (100’s count) and subjected for accelerated stability studies at 40˚C/75% RH for 3


55


months. The drug content and in vitro drug release was found to be 97, 92, 90, 93 for initial,

1st month, 2

nd month, and 3

rd month respectively. The results of stability studies indicated that

the developed product was stable.

DIVALPROEX SODIUM ER CONCLUSION

56


7. CONCLUSION

The extended release tablets of divalproex sodium were prepared and different

formulations were subjected to various evaluation tests such as thickness, diameter, and

uniformity of weight and drug content, hardness friability, and in-vitro dissolution. The

results obtained were found to be within specification limits.

Of all the formulations formulation F8 complies as per in-house specification with the

innovator sample. And hence, optimized batch (F8) is concluded as optimized formula due to

its good in-vitro release characteristics.

The formulated tablets were able to meet the set objectives. As the drug release was

found to be constant over a 24 hour period and found to be stable.

DIVALPROEX SODIUM ER SUMMARY

57


8. SUMMARY

The present work aims to formulate extended release matrix tablets of Divalproex

sodium with a view to reduce the incidence of side effects associated with conventional

tablets and reduce the frequency of drug administration thereby to improve patient

compliance.

The calibration curve of Divalproex sodium was constructed by UV-

spectrophotometer. It was found that the curve was linear over a concentration range of 2-10

μg/ml with r2 value of 0.997.




Hausner’s ratio = 1.292%).

The drug excipient compatibility studies indicated that there was no physical change

in the drug when mixed with various excipients and subjected to accelerated stress conditions

(400C/75%RH) upto 4weeks.

X-Ray diffraction studies of the drug and excipients indicated that the characteristic

peaks of the drug were retained in the mixture there by indicating absence of interaction

between the drug and the excipients.

The intention of present work was to develop a product having release profile similar to the

innovator product. Hence the innovator product (DEPAKOTE®ER) was evaluated to

determine the characteristics of final product. Based on the percentage drug release of the

innovator product, the target release was calculated.

In formulation F8 the concentration of starch 1500 was increased to 5.65% and the

drug concentration was kept to 53.27% all other concentration were kept same as that of F4.

Initially high drug concentration was observed but maintained all over the time period. The

percentage drug release for this formulation was maintained with innovator in close range.

Hence, formulation F8 was considered to be the optimized formulation in which

the release profile was found to be very close to that of innovator (%DR= 98).

DIVALPROEX SODIUM ER SUMMARY

58


The optimized final formulation was packed in HDPE heavy weight container with 1g silica

gel (100’s count) and subjected for accelerated stability studies at 40˚C/75% RH for 3

months. The drug content and in vitro drug release was found to be 97, 92, 90, 93 for initial,

1st month, 2

nd month, and 3

rd month respectively. The results of stability studies indicated that

the developed product was stable.

Once-a-day Divalproex sodium extended release tablets would be thus helpful in reducing

dosing frequency and decreasing the associated side effects, likewise increasing patient

compliance.

DIVALPROEX SODIUM ER REFERENCES

59


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divalproex sodium

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